This application relates to a power transfer between two power sources and an accessory bus, such as may be associated with an aircraft.
Modern aircraft typically power any number of applications. Generators generate power and deliver that power to power buses that run across the length of the aircraft. In addition, power is supplied for functions such as providing air, light, etc., to the aircraft cabin. This is but a short listing of potential components powered from the bus.
In modern aircraft, an auxiliary power unit (APU) includes a source of power, such as a small gas turbine engine, which drives a generator.
Gas turbine engines on the aircraft also drive generators, to produce electric power to be delivered to the bus. When the aircraft is on the ground, the main gas turbine engines have yet to be started, and are not delivering significant power. Instead, at that time, power is supplied by the APU. At some point, power is transferred to the bus by opening a switch associated with the APU, and closing a switch to deliver power from the main gas turbine engine generators.
Such a point in time is typically associated with an apparent break to the aircraft occupants. As an example, lights may flicker, air flow may stop momentarily, etc.